(1) Field of the Invention
This invention is related to semiconductors and, more particularly, to an ultra low resistance ohmic contact to the semiconductors such as gallium arsenide.
(2) Description of the Prior Art
In order to form low resistance ohmic contacts to semiconductors that have surface states (extrinsic or intrinsic) which pin the Fermi level inside the forbidden zone of the semiconductor, it is usually necessary to alloy complex metallurgical layers. Such a process is time consuming, expensive and is not completely reliable. Furthermore, it does not provide contacts which are resistant to degradation under high temperature operations. Furthermore, it is usually difficult to control the morphology of the alloy. Therefore, it is desirable to have a low resistance ohmic contact for semiconductors which can be made without melting a eutectic mixture of a metal such as gold, with germanium (which acts as an impurity) on a semiconductor such as GaAs.